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Rate of crustal shortening and non-Coulomb behaviour of an active accretionary wedge - the folded fluvial terraces in Makran (SE, Iran)

  • We surveyed fluvial terraces to decipher the Quaternary increment of crustal shortening and shortening rate in the on-shore Makran Accretionary Wedge. We focused on three major catchment basins and associated fold systems. Terrace profiles reconstructed from differential GPS measurements combined with DEM revealed two regional dominant wavelengths, about 5 km in the northern part of the study area and about 15 km to the south. These two wavelengths suggest the existence of two active decollement layers at two rooting depths. The average shortening rate due to folding is estimated at 0.8-1.2 mm/a over the last 130 ka. This accounts for 10-15% of the shortening rate (similar to 8 mm/a) given by kinematic GPS measurements between Chabahar and Bazman and 3% of the convergence between Arabia and Eurasia, across the Makran subduction zone. Despite active deformation and a relatively high shortening rate, the geophysical record shows nearly absent seismic activity in Makran. We propose that strain accumulated in folds over intermediateWe surveyed fluvial terraces to decipher the Quaternary increment of crustal shortening and shortening rate in the on-shore Makran Accretionary Wedge. We focused on three major catchment basins and associated fold systems. Terrace profiles reconstructed from differential GPS measurements combined with DEM revealed two regional dominant wavelengths, about 5 km in the northern part of the study area and about 15 km to the south. These two wavelengths suggest the existence of two active decollement layers at two rooting depths. The average shortening rate due to folding is estimated at 0.8-1.2 mm/a over the last 130 ka. This accounts for 10-15% of the shortening rate (similar to 8 mm/a) given by kinematic GPS measurements between Chabahar and Bazman and 3% of the convergence between Arabia and Eurasia, across the Makran subduction zone. Despite active deformation and a relatively high shortening rate, the geophysical record shows nearly absent seismic activity in Makran. We propose that strain accumulated in folds over intermediate decollement levels within a thick, incompletely lithified sedimentary cover explains the essentially aseismic, recent tectonics in this region. The importance of folds points to imperfect Coulomb behaviour of the wedge. (C) 2012 Elsevier B.V. All rights reserved.show moreshow less

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Metadaten
Author:Negar Haghipour, Jean-Pierre Burg, Florian Kober, Gerold Zeilinger, Susan Ivy-Ochs, Peter W. Kubik, Mohammad Faridi
DOI:https://doi.org/10.1016/j.epsl.2012.09.001
ISSN:0012-821X (print)
Parent Title (English):Earth & planetary science letters
Publisher:Elsevier
Place of publication:Amsterdam
Document Type:Article
Language:English
Year of first Publication:2012
Year of Completion:2012
Release Date:2017/03/26
Tag:Be-10 dating; accretionary wedge; fluvial terraces; shortening rate
Volume:355
Pagenumber:12
First Page:187
Last Page:198
Funder:ETH project [0-20481-08]; Swiss National Fond project [2-77644-09]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Ernährungswissenschaft
Peer Review:Referiert